Dielectric, ferroelectric, piezoelectric properties, and conduction behavior of (Bi_0.5Na_0.5)_0.94+xBa_0.06TiO₃ ceramics

The electrical properties and conduction behavior of (Bi_0.5Na_0.5)_0.94+xBa_0.06TiO₃ (x = 0, 0.01; denoted as BNBT, BNBT + 0.01BN) ceramics were studied. Both samples demonstrated a single-phase perovskite structure. Compared to the BNBT sample, the BNBT + 0.01BN sample showed a reduction in grain size and decreased values for Curie temperature (T_m) and depolarization temperature (T_d). Normalized spectroscopic plots of M"/M"_max and Z"/Z"_max revealed a single relaxation peak. The complex impedance plots were modeled using an equivalent circuit, and the grain resistance (R_g) decreases with increasing temperature. At 500 °C, the R_g values for BNBT and BNBT + 0.01BN samples were 339.97 and 886.98 kΩ × cm, respectively. Jonscher’s law was applied to fit the AC conductivity, and the obtained n values indicated different conduction mechanisms for the two samples. Additionally, the conduction activation energy (E_con) for DC conductivity followed the Arrhenius relation. Introducing a small (Bi,Na) excess suppresses oxygen and cation vacancies, significantly increasing resistivity. Consequently, the BNBT + 0.01BN sample exhibited excellent remanent polarization (P_r) of 34.2 μC/cm² and piezoelectric constant (d₃₃) of 135 pC/N.